1. Field of the Invention
The present invention relates generally to power tools, particularly hedge trimmers, and specifically to an extended reach hedge trimmer with a pivotally connected and adjustable cutting head providing improved controlled cutting plane adjustability and safety of operation. The present invention utilizes a yoke pivotally connected to a powerhead which allows the powerhead to pivot about an axis of rotation on the yoke and which also provides electrical cord strain relief in embodiments using an electric motor. The invention further includes a friction brake for preventing free rotation of the powerhead about the axis to enhance operational safety of the trimmer.
2. Description of the Related Art
Motorized trimmers for cutting hedges and shrubs are widely recognized as being very useful in maintaining their aesthetically pleasing appearance. Typically, these hedge trimming devices include an engine or motor, which may be powered either electrically or through an internal combustion process, a handle apparatus and a cutting unit. Early versions of such hedge trimming devices typically include a one-sided reciprocating blade assembly and a drive mechanism or gear box which is in turn driven by the motor.
More recently, hedge trimmers utilizing a two-sided reciprocating blade means have been developed. The two-sided blade means is an improvement to trimmers since it permits a user to trim hedges while guiding the cutting means in either direction across the surface of the hedges. Additionally, the interval between sharpening of the reciprocating blades can be increased if both sides of the two-sided reciprocating blade means are evenly used.
There are known in the art numerous commercially available hedge trimmers having two-sided reciprocating cutting blades driven by an electric motor or an internal combustion engine. These trimmers typically have the cutting blade assembly and the motor positioned in close proximity to each other cantilevered off the forward end of the trimmer handle. This unbalanced arrangement requires the user of the trimmer to support the cantilevered weight of both the motor and reciprocating blade assembly while using the trimmer, thus tiring the user more quickly. Trimmers so arranged typically include a secondary handle to permit the user to more comfortably use the trimming device. These devices require a user to hold the trimmer with both hands at all times in order to support this unbalanced configuration.
Electric hedge trimmers are generally designed to be held directly by a user and used in the immediate proximity of a user. If a user wishes to trim a hedge which is above the height of the user's head, the typical procedure is to use a step ladder or other height extending device such as a cherry picker. The use of a step ladder involves known safety hazards and devices such as cherry pickers are not available at reasonable cost for the average homeowner or professional gardener. With the increased use of shaped trees in landscaping, the need for trimming at a distance beyond the reach of the user has become more widespread. The use of a step ladder, particularly when combined with the necessity to reach away from the step ladder while holding the trimmer, creates a substantial safety hazard. The ground under a hedge or tree is typically not level and in the case of a hedge there is nothing sturdy against which a ladder may be leaned.
Current hand-held hedge trimmers are therefore limited in their ability to trim hedges or shrubs which are excessively tall or broad. Extended reach hedge trimmers do exist that enable users to better address those difficult trimming applications, but these units are gas engine powered and typically much more expensive than the common, electric hand-held hedge trimmers.
There has been some work in the area of electric, extended reach hedge trimmers, and they basically fall into two categories. One category is an accessory extension handle for a traditional, hand-held hedge trimmer. In the past various extension poles have been proposed which typically would be screwed on to the handle of the tool after which the tool would be plugged in and operated at a remote distance. Such tools, however, have not enjoyed widespread use for several reasons. A common drawback of such devices when used with electrically powered tools is that the electrical cord hangs down from the tool and becomes easily ensnarled in the branches, making it surprisingly easy for the cord to become tangled in the branches which are being trimmed and to actually trim through the electrical cord itself. Furthermore, most such prior art devices have no ready means for turning the tool on and off, which for most trimming operations is a highly desirable feature.
This approach has other disadvantages in that the weight of the traditional, hand-held hedge trimmer exerts too much of a moment on the user when attached to an extended length handle. This approach also requires some additional means to depress the actuation switch of the hedge trimmer, and requires a secondary actuation switch in the extension pole. This approach also limits the variety of cutting planes that a user can create with the cutter bar of the hedge trimmer, thereby further limiting its effectiveness.
A second approach is to construct an extended reach hedge trimmer where the electric motor and the cutter head are separated. The electric motor is located on the lower end of an extended length handle, and the cutter head is on the upper end of the extended length handle. The output of the electric motor is connected to the cutter blade input by means of a flexible shaft that runs, through the extended handle, between the cutter head and the electric motor. The drawback of this approach is the expense of the flexible metal shaft and the expense of separate housings for the cutter head and the motor housing. Both of these approaches are limited in that a user who has both low to medium size shrubs and large, tall shrubs would need a traditional, hand-held hedge trimmer and an extended reach hedge trimmer.